1. Field of the Invention
This invention relates to a suspension-traction total control system for a vehicle.
2. Description of the Prior Art
As disclosed, for instance, in U.S. Pat. No. 4,830,397, there has been known an active suspension system (ACS system) which comprises cylinder devices provided between the vehicle body and the respective wheels and in which hydraulic fluid is fed to or discharged from each of the cylinder devices separately from the other cylinder devices, whereby the suspension properties are changed so that the vehicle body is kept horizontal, and driving comfort and running stability are improved Further, in U.S. Pat. No. 4,805,102, it is disclosed that the suspension properties are turned hard when slip of the driving wheels reaches a predetermined value during acceleration of the vehicle, thereby quickly suppressing inclination of the vehicle body caused by the acceleration slip control.
When the driving torque transmitted to the driving wheels is excessively large relative to the frictional resistance of road surface, the driving wheels will race and the driving force is lost, whereby the traction lowers. There has been known a traction control system (TRC system) which lowers the engine output power and brakes the driving wheels when the driving wheels slip, thereby controlling the driving torque to an optimal value and ensuring traction. (See, for instance, Japanese Unexamined Patent Publication No. 57(1982)-22948)
In the case of a vehicle provided with both the ACS system and the TRC system, generally the suspension control and the traction control are effected separately from each other.
However, since the part of the vehicle body on the driving wheels moves up and down in response to abrupt change of the driving torque during the traction control, it is preferred that the suspension properties be changed taking into account this fact.